The limit values differ from each other due to the amount of methane and hydrogen that bacteria are producing during the metabolisation of lactose. Normally, there isn't any or there is some methane produced - even with lactose intolerance. Only a few people have been observed who have both methane and hydrogen production with lactose intolerance. In order to cover all affected people we measure both values. Most people show little amounts of hydrogen and no methane at all in the exhaled air. Once either one or both of the values are exceeded, it can be lactose intolerance. That is why both values are equally important. If only production of only one of the gases is detected, this only means that the bacteria in the gut are producing the gas during metabolisation. In any case this indicates a lactose intolerance.